Git submodules update after devcontainer starts

Question

I'm trying to create a devcontainer that automatically initializes and updates the submodules when the repository is first cloned.

I have a repository on GitLab with different submodules and a devcontainer.json file:

.
├── submodule1
├── submodule2
├── submodule3
└── .devcontainer
    ├── devcontainer.json
    └── modules.sh

Content of devcontainer.json:

{
    "name": "Ubuntu",
    "image": "mcr.microsoft.com/devcontainers/base:jammy",
    "postCreateCommand": "while [ -z \"$(ls ~/.vscode-server/extensions | grep gitlab)\" ] ; do sleep 1 ; done && sh ${containerWorkspaceFolder}/.devcontainer/modules.sh",
    "customizations": {
        "vscode": {
            "extensions": [
                "gitlab.gitlab-workflow"
            ]
        }
    }

Content of modules.sh:

#!/bin/sh

git submodule init
git submodule update

Usually, I use the VSCode GitLab Workflow extension because it allows me to avoid in typing the credentials every time I want to commit something.

When I start the container, the postCreateCommand asks for credentials and blocks for input, while if I launch the git submodule init and update commands by hand after the container is launched, it works.

How can I get all the environment autometically configured without requiring git to ask for credential?